1
|
Aubier TG, Galipaud M. Senescence evolution under the catastrophic accumulation of deleterious mutations. Evol Lett 2024; 8:212-221. [PMID: 38525026 PMCID: PMC10959475 DOI: 10.1093/evlett/qrad050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/25/2023] [Accepted: 09/19/2023] [Indexed: 03/26/2024] Open
Abstract
For aging to evolve, selection against mortality must decrease with age. This prevailing view in the evolutionary theory of senescence posits that mutations with deleterious effects happening late in life-when purging selection is weak-may become fixed via genetic drift in the germline, and produce a senescent phenotype. Theory, however, has focused primarily on growing populations and the fate of single deleterious mutations. In a mathematical model, we demonstrate that relaxing both of these simplifying assumptions leads to unrealistic outcomes. In density-regulated populations, previously fixed deleterious mutations should promote the fixation of other deleterious mutations that lead to senescence at ever younger ages, until death necessarily occurs at sexual maturity. This sequential fixation of deleterious mutations is not promoted by a decrease in population size, but is due to a change in the strength of selection. In an individual-based model, we also show that such evolutionary dynamics should lead to the extinction of most populations. Our models therefore make rather unrealistic predictions, underlining the need for a reappraisal of current theories. In this respect, we have further assumed in our models that the deleterious effects of mutations can only occur at certain ages, marked, for instance, by somatic or physiological changes. Under this condition, we show that the catastrophic accumulation of deleterious mutations in the germline can stop. This new finding emphasizes the importance of investigating somatic factors, as well as other mechanisms underlying the deleterious effects of mutations, to understand senescence evolution. More generally, our model therefore establishes that patterns of senescence in nature depend not only on the decrease in selection strength with age but also on any mechanism that stops the catastrophic accumulation of mutations.
Collapse
Affiliation(s)
- Thomas G Aubier
- Laboratoire Évolution and Diversification Biologique, Université Paul Sabatier Toulouse III, UMR 5174, CNRS/IRD, 31077 Toulouse, France
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - Matthias Galipaud
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Swiss Data Science Center, ETH, Zurich, Switzerland
| |
Collapse
|
2
|
Travis J, Bassar RD, Coulson T, Lopez-Sepulcre A, Reznick D. Population Regulation and Density-Dependent Demography in the Trinidadian Guppy. Am Nat 2023; 202:413-432. [PMID: 37792920 DOI: 10.1086/725796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
AbstractClassic theory for density-dependent selection for delayed maturation requires that a population be regulated through some combination of adult fecundity and/or juvenile survival. We tested whether those demographic conditions were met in four experimental populations of Trinidadian guppies in which delayed maturation of males evolved when the densities of those populations became high. We used monthly mark-recapture data to examine population dynamics and demography in these populations. Three of the four populations displayed clear evidence of regulation. In all four populations, monthly adult survival rates were independent of biomass density or actually increased with increased biomass density. Juvenile recruitment, which is a combination of adult fecundity and juvenile survival, decreased as biomass density increased in all four populations. Demography showed marked seasonality, with greater survival and higher recruitment in the dry season than the wet season. Population regulation via juvenile recruitment supports the hypothesis that density-dependent selection was responsible for the evolution of delayed maturity in males. This body of work represents one of the few complete tests of density-dependent selection theory.
Collapse
|
3
|
Koivu‐Jolma M, Kortet R, Vainikka A, Kaitala V. Crayfish population size under different routes of pathogen transmission. Ecol Evol 2023; 13:e9647. [PMID: 36620414 PMCID: PMC9817202 DOI: 10.1002/ece3.9647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 11/25/2022] [Accepted: 12/02/2022] [Indexed: 01/09/2023] Open
Abstract
We present an epidemiological model for the crayfish plague, a disease caused by an invasive oomycete Aphanomyces astaci, and its general susceptible freshwater crayfish host. The pathogen shows high virulence with resulting high mortality rates in freshwater crayfishes native to Europe, Asia, Australia, and South America. The crayfish plague occurrence shows complicated dynamics due to the several types of possible infection routes, which include cannibalism and necrophagy. We explore this complexity by addressing the roles of host cannibalism and the multiple routes of transmission through (1) environment, (2) contact, (3) cannibalism, and (4) scavenging of infected carcasses. We describe a compartment model having six classes of crayfish and a pool of crayfish plague spores from a single nonevolving strain. We show that environmental transmission is the decisive factor in the development of epidemics. Compared with a pathogen-free crayfish population, the presence of the pathogen with a low environmental transmission rate, regardless of the contact transmission rate, decreases the crayfish population size with a low risk of extinction. Conversely, a high transmission rate could drive both the crayfish and pathogen populations to extinction. High contact transmission rate with a low but nonzero environmental transmission rate can have mixed outcomes from extinction to large healthy population, depending on the initial values. Scavenging and cannibalism have a relevant role only when the environmental transmission rate is low, but scavenging can destabilize the system by transmitting the pathogen from a dead to a susceptible host. To the contrary, cannibalism stabilizes the dynamics by decreasing the proportion of infected population. Our model provides a simple tool for further analysis of complex host parasite dynamics and for the general understanding of crayfish disease dynamics in the wild.
Collapse
Affiliation(s)
- Mikko Koivu‐Jolma
- Department of Physics, Faculty of ScienceUniversity of HelsinkiHelsinkiFinland
| | - Raine Kortet
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
| | - Anssi Vainikka
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
| | - Veijo Kaitala
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
| |
Collapse
|
4
|
Rosenheim JA, Schreiber SJ. Pathways to the density-dependent expression of cannibalism, and consequences for regulated population dynamics. Ecology 2022; 103:e3785. [PMID: 35818739 DOI: 10.1002/ecy.3785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 04/13/2022] [Accepted: 04/21/2022] [Indexed: 12/13/2022]
Abstract
Cannibalism, once viewed as a rare or aberrant behavior, is now recognized to be widespread and to contribute broadly to the self-regulation of many populations. Cannibalism can produce endogenous negative feedback on population growth because it is expressed as a conditional behavior, responding to the deteriorating ecological conditions that flow, directly or indirectly, from increasing densities of conspecifics. Thus, cannibalism emerges as a strongly density-dependent source of mortality. In this synthesis, we review recent research that has revealed a rich diversity of pathways through which rising density elicits increased cannibalism, including both factors that (a) elevate the rate of dangerous encounters between conspecifics and (b) enhance the likelihood that such encounters will lead to successful cannibalistic attacks. These pathways include both features of the autecology of cannibal populations and features of interactions with other species, including food resources and pathogens. Using mathematical models, we explore the consequences of including density-dependent cannibal attack rates on population dynamics. The conditional expression of cannibalism generally enhances stability and population regulation in single-species models but also may increase opportunities for alternative states and prey population escape from control by cannibalistic predators.
Collapse
Affiliation(s)
- Jay A Rosenheim
- Department of Entomology and Nematology, University of California, Davis, California, USA
| | - Sebastian J Schreiber
- Department of Evolution and Ecology, University of California, Davis, California, USA
| |
Collapse
|
5
|
Healy BD, Budy P, Conner MM, Omana Smith EC. Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations. Ecol Appl 2022. [PMID: 35403769 DOI: 10.6084/m9.figshare.c.5805593.v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking owing to difficulties in long-term monitoring of rare species. Translocations, here defined as the transfer of wild-captured individuals from source populations to new habitats, are widely used for species conservation, but outcomes are often minimally monitored, and translocations that are monitored often fail. To improve our understanding of how translocated populations respond to environmental variation, we developed and tested hypotheses related to intrinsic (density dependent) and extrinsic (introduced rainbow trout Oncorhynchus mykiss, stream flow and temperature regime) causes of vital rate variation in endangered humpback chub (Gila cypha) populations translocated to Colorado River tributaries in the Grand Canyon (GC), USA. Using biannual recapture data from translocated populations over 10 years, we tested hypotheses related to seasonal somatic growth, and recruitment and population growth rates with linear mixed-effects models and temporal symmetry mark-recapture models. We combined data from recaptures and resights of dispersed fish (both physical captures and continuously recorded antenna detections) from throughout GC to test survival hypotheses, while accounting for site fidelity, using joint live-recapture/live-resight models. While recruitment only occurred in one site, which also drove population growth (relative to survival), evidence supported hypotheses related to density dependence in growth, survival, and recruitment, and somatic growth and recruitment were further limited by introduced trout. Mixed-effects models explained between 67% and 86% of the variation in somatic growth, which showed increased growth rates with greater flood-pulse frequency during monsoon season. Monthly survival was 0.56-0.99 and 0.80-0.99 in the two populations, with lower survival during periods of higher intraspecific abundance and low flood frequency. Our results suggest translocations can contribute toward the recovery of large-river fishes, but continued suppression of invasive fishes to enhance recruitment may be required to ensure population resilience. Furthermore, we demonstrate the importance of flooding to population demographics in food-depauperate, dynamic, invaded systems.
Collapse
Affiliation(s)
- Brian D Healy
- Department of Watershed Sciences and the Ecology Center, Utah State University, Logan, Utah, USA
- Native Fish Ecology and Conservation Program, Division of Science and Resource Management, Grand Canyon National Park, National Park Service, Flagstaff, Arizona, USA
| | - Phaedra Budy
- Department of Watershed Sciences and the Ecology Center, Utah State University, Logan, Utah, USA
- United States Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Department of Watershed Sciences, Utah State University, Logan, Utah, USA
| | - Mary M Conner
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, Utah, USA
| | - Emily C Omana Smith
- Native Fish Ecology and Conservation Program, Division of Science and Resource Management, Grand Canyon National Park, National Park Service, Flagstaff, Arizona, USA
| |
Collapse
|
6
|
Healy BD, Budy P, Conner MM, Omana Smith EC. Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations. Ecol Appl 2022; 32:e2635. [PMID: 35403769 PMCID: PMC9541007 DOI: 10.1002/eap.2635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Revised: 01/25/2022] [Accepted: 02/24/2022] [Indexed: 05/14/2023]
Abstract
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking owing to difficulties in long-term monitoring of rare species. Translocations, here defined as the transfer of wild-captured individuals from source populations to new habitats, are widely used for species conservation, but outcomes are often minimally monitored, and translocations that are monitored often fail. To improve our understanding of how translocated populations respond to environmental variation, we developed and tested hypotheses related to intrinsic (density dependent) and extrinsic (introduced rainbow trout Oncorhynchus mykiss, stream flow and temperature regime) causes of vital rate variation in endangered humpback chub (Gila cypha) populations translocated to Colorado River tributaries in the Grand Canyon (GC), USA. Using biannual recapture data from translocated populations over 10 years, we tested hypotheses related to seasonal somatic growth, and recruitment and population growth rates with linear mixed-effects models and temporal symmetry mark-recapture models. We combined data from recaptures and resights of dispersed fish (both physical captures and continuously recorded antenna detections) from throughout GC to test survival hypotheses, while accounting for site fidelity, using joint live-recapture/live-resight models. While recruitment only occurred in one site, which also drove population growth (relative to survival), evidence supported hypotheses related to density dependence in growth, survival, and recruitment, and somatic growth and recruitment were further limited by introduced trout. Mixed-effects models explained between 67% and 86% of the variation in somatic growth, which showed increased growth rates with greater flood-pulse frequency during monsoon season. Monthly survival was 0.56-0.99 and 0.80-0.99 in the two populations, with lower survival during periods of higher intraspecific abundance and low flood frequency. Our results suggest translocations can contribute toward the recovery of large-river fishes, but continued suppression of invasive fishes to enhance recruitment may be required to ensure population resilience. Furthermore, we demonstrate the importance of flooding to population demographics in food-depauperate, dynamic, invaded systems.
Collapse
Affiliation(s)
- Brian D. Healy
- Department of Watershed Sciences and the Ecology CenterUtah State UniversityLoganUtahUSA
- Native Fish Ecology and Conservation Program, Division of Science and Resource ManagementGrand Canyon National Park, National Park ServiceFlagstaffArizonaUSA
| | - Phaedra Budy
- Department of Watershed Sciences and the Ecology CenterUtah State UniversityLoganUtahUSA
- United States Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Department of Watershed SciencesUtah State UniversityLoganUtahUSA
| | - Mary M. Conner
- Department of Wildland Resources and the Ecology CenterUtah State UniversityLoganUtahUSA
| | - Emily C. Omana Smith
- Native Fish Ecology and Conservation Program, Division of Science and Resource ManagementGrand Canyon National Park, National Park ServiceFlagstaffArizonaUSA
| |
Collapse
|
7
|
McIntosh AR, Greig HS, Howard S. Regulation of open populations of a stream insect through larval density-dependence. J Anim Ecol 2022; 91:1582-1595. [PMID: 35362147 PMCID: PMC9541859 DOI: 10.1111/1365-2656.13696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 03/15/2022] [Indexed: 12/01/2022]
Abstract
In organisms with complex life cycles, the various stages occupy different habitats creating demographically open populations. The dynamics of these populations will depend on the occurrence and timing of stochastic influences relative to demographic density dependence, but understanding of these fundamentals, especially in the face of climate warming, has been hampered by the difficulty of empirical studies. Using a logically feasible organism, we conducted a replicated density‐perturbation experiment to manipulate late‐instar larvae of nine populations of a stream caddisfly, Zelandopsyche ingens, and measured the resulting abundance over 2 years covering the complete life cycle of one cohort to evaluate influences on dynamics. Negative density feedback occurred in the larval stage, and was sufficiently strong to counteract variation in abundance due to manipulation of larval density, adult caddis dispersal in the terrestrial environment as well as downstream drift of newly hatched and older larvae in the current. This supports theory indicating regulation of open populations must involve density dependence in local populations sufficient to offset variability associated with dispersal, especially during recruitment, and pinpoints the occurrence to late in the larval life cycle and driven by food resource abundance. There were large variations in adult, egg mass and early instar abundance that were not related to abundance in the previous stage, or the manipulation, pointing to large stochastic influences. Thus, the results also highlight the complementary nature of stochastic and deterministic influences on open populations. Such density dependence will enhance population persistence in situations where variable dispersal and transitioning between life stages frequently creates mismatches between abundance and the local availability of resources, such as might become more common with climate warming.
Collapse
Affiliation(s)
- Angus R McIntosh
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
| | - Hamish S Greig
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.,Present address: School of Biology and Ecology, University of Maine, ME, USA
| | - Simon Howard
- Manaaki Whenua Landcare Research, Lincoln, New Zealand
| |
Collapse
|
8
|
Navarrete SA, Barahona M, Weidberg N, Broitman BR. Climate change in the coastal ocean: shifts in pelagic productivity and regionally diverging dynamics of coastal ecosystems. Proc Biol Sci 2022; 289:20212772. [PMID: 35259989 PMCID: PMC8914614 DOI: 10.1098/rspb.2021.2772] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Climate change has led to intensification and poleward migration of the Southeastern Pacific Anticyclone, forcing diverging regions of increasing, equatorward and decreasing, poleward coastal phytoplankton productivity along the Humboldt Upwelling Ecosystem, and a transition zone around 31° S. Using a 20-year dataset of barnacle larval recruitment and adult abundances, we show that striking increases in larval arrival have occurred since 1999 in the region of higher productivity, while slower but significantly negative trends dominate poleward of 30° S, where years of recruitment failure are now common. Rapid increases in benthic adults result from fast recruitment-stock feedbacks following increased recruitment. Slower population declines in the decreased productivity region may result from aging but still reproducing adults that provide temporary insurance against population collapses. Thus, in this region of the ocean where surface waters have been cooling down, climate change is transforming coastal pelagic and benthic ecosystems through altering primary productivity, which seems to propagate up the food web at rates modulated by stock-recruitment feedbacks and storage effects. Slower effects of downward productivity warn us that poleward stocks may be closer to collapse than current abundances may suggest.
Collapse
Affiliation(s)
- Sergio A Navarrete
- Estación Costera de Investigaciones Marinas, Las Cruces, Center for Applied Ecology and Sustainability (CAPES), and Millennium Nucleus for Ecology and Conservation of Temperate Mesophotic Reefs (NUTME), Pontificia Universidad Católica de Chile, Santiago, Chile.,Millennium Institute for Coastal Socio-Ecology (SECOS), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mario Barahona
- Estación Costera de Investigaciones Marinas, Las Cruces, Center for Applied Ecology and Sustainability (CAPES), and Millennium Nucleus for Ecology and Conservation of Temperate Mesophotic Reefs (NUTME), Pontificia Universidad Católica de Chile, Santiago, Chile.,Departamento de Ciencias, Facultad de Artes Liberales, Nucleo Milenio UPWELL, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar, Chile
| | - Nicolas Weidberg
- Estación Costera de Investigaciones Marinas, Las Cruces, Center for Applied Ecology and Sustainability (CAPES), and Millennium Nucleus for Ecology and Conservation of Temperate Mesophotic Reefs (NUTME), Pontificia Universidad Católica de Chile, Santiago, Chile.,Department of Biological Sciences, University of South Carolina, Columbia, SC, USA.,Facultad de Ciencias del Mar, Universidad de Vigo, Vigo, Galicia, Spain
| | - Bernardo R Broitman
- Millennium Institute for Coastal Socio-Ecology (SECOS), Pontificia Universidad Católica de Chile, Santiago, Chile.,Departamento de Ciencias, Facultad de Artes Liberales, Nucleo Milenio UPWELL, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar, Chile
| |
Collapse
|
9
|
Li W, Niu C, Bian S. Sex ratio in the mother's environment affects offspring population dynamics: maternal effects on population regulation. Proc Biol Sci 2022; 289:20212530. [PMID: 35232242 PMCID: PMC8889200 DOI: 10.1098/rspb.2021.2530] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Classic population regulation theories usually concern the influence of immediate factors on current populations, but studies investigating the effect of parental environment factors on their offspring populations are scarce. The maternal environments can affect offspring life-history traits across generations, which may affect population dynamics and be a mechanism of population regulation. In cyclical parthenogens, sexual reproduction is typically linked with dormancy, thereby providing a negative feedback to population growth. In this study, we manipulated population sex ratios in the mother's environment to investigate whether this factor affected future population dynamics by regulating offspring sexual reproduction in the rotifer Brachionus calyciflorus. Compared with females in male-biased environments, those in female-biased environments produced fewer mictic (sexual) offspring, and their amictic (asexual) offspring also produced a lower proportion of mictic females at a gradient of population densities. Moreover, populations that were manipulated under male-biased conditions showed significantly smaller population sizes than those under female-biased conditions. Our results indicated that in cyclical parthenogens, mothers could adjust the sexual reproduction of their offspring in response to the current population sex ratio, thus providing fine-scale regulation of population dynamics in addition to population density.
Collapse
Affiliation(s)
- Wenjie Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Cuijuan Niu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Shijun Bian
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, People's Republic of China
| |
Collapse
|
10
|
Goto D, Filin AA, Howell D, Bogstad B, Kovalev Y, Gjøsaeter H. Tradeoffs of managing cod as a sustainable resource in fluctuating environments. Ecol Appl 2022; 32:e2498. [PMID: 34787943 DOI: 10.1002/eap.2498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 06/13/2023]
Abstract
Sustainable human exploitation of living marine resources stems from a delicate balance between yield stability and population persistence to achieve socioeconomic and conservation goals. But our imperfect knowledge of how oceanic oscillations regulate temporal variation in an exploited species can obscure the risk of missing management targets. We illustrate how applying a management policy to suppress fluctuations in fishery yield in variable environments (prey density and regional climate) can present unintended outcomes in harvested predators and the sustainability of harvesting. Using Atlantic cod (Gadus morhua, an apex predatory fish) in the Barents Sea as a case study we simulate age-structured population and harvest dynamics through time-varying, density-dependent and density-independent processes with a stochastic, process-based model informed by 27-year monitoring data. In this model, capelin (Mallotus villosus, a pelagic forage fish), a primary prey of cod, fluctuations modulate the strength of density-dependent regulation primarily through cannibalistic pressure on juvenile cod survival; sea temperature fluctuations modulate thermal regulation of cod feeding, growth, maturation, and reproduction. We first explore how capelin and temperature fluctuations filtered through cod intrinsic dynamics modify catch stability and then evaluate how management to suppress short-term variability in catch targets alters overharvest risk. Analyses revealed that suppressing year-to-year catch variability impedes management responses to adjust fishing pressure, which becomes progressively out of sync with variations in cod abundance. This asynchrony becomes amplified in fluctuating environments, magnifying the amplitudes of both fishing pressure and cod abundance and then intensifying the density-dependent regulation of juvenile survival through cannibalism. Although these transient dynamics theoretically give higher average catches, emergent, quasicyclic behaviors of the population would increase long-term yield variability and elevate overharvest risk. Management strategies that overlook the interplay of extrinsic (fishing and environment) and intrinsic (life history and demography) fluctuations thus can inadvertently destabilize fish stocks, thereby jeopardizing the sustainability of harvesting. These policy implications underscore the value of ecosystem approaches to designing management measures to sustainably harvest ecologically connected resources while achieving socioeconomic security.
Collapse
Affiliation(s)
- Daisuke Goto
- Institute of Marine Research, P.O. Box 1870, Nordnes, 5817, Bergen, Norway
| | - Anatoly A Filin
- Polar Branch of the Federal State Budget Scientific Institution, Russian Federal Research Institute of Fisheries and Oceanography ("PINRO" named after N.M. Knipovich), Akademik Knipovich Street 6, Murmansk, 183038, Russia
| | - Daniel Howell
- Institute of Marine Research, P.O. Box 1870, Nordnes, 5817, Bergen, Norway
| | - Bjarte Bogstad
- Institute of Marine Research, P.O. Box 1870, Nordnes, 5817, Bergen, Norway
| | - Yury Kovalev
- Polar Branch of the Federal State Budget Scientific Institution, Russian Federal Research Institute of Fisheries and Oceanography ("PINRO" named after N.M. Knipovich), Akademik Knipovich Street 6, Murmansk, 183038, Russia
| | - Harald Gjøsaeter
- Institute of Marine Research, P.O. Box 1870, Nordnes, 5817, Bergen, Norway
| |
Collapse
|
11
|
Devers PK, Emmet RL, Boomer GS, Zimmerman GS, Royle JA. Evaluation of a two-season banding program to estimate and model migratory bird survival. Ecol Appl 2021; 31:e02425. [PMID: 34296480 DOI: 10.1002/eap.2425] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 02/22/2021] [Accepted: 03/22/2021] [Indexed: 06/13/2023]
Abstract
The management of North American waterfowl is predicated on long-term, continental-scale banding implemented prior to the hunting season (i.e., July-September) and subsequent reporting of bands recovered by hunters. However, single-season banding and encounter operations have a number of characteristics that limit their application to estimating demographic rates and evaluating hypothesized limiting factors throughout the annual cycle. We designed and implemented a two-season banding program for American Black Ducks (Anas rubripes), Mallards (A. platyrhynchos), and hybrids in eastern North America to evaluate potential application to annual life cycle conservation and sport harvest management. We assessed model fit and compared estimates of annual survival among data types (i.e., pre-hunting season only [July-September], post-hunting season only [January-March], and two-season [pre- and post-hunting season]) to evaluate model assumptions and potential application to population modeling and management. There was generally high agreement between estimates of annual survival derived using two-season and pre-season only data for all age and sex cohorts. Estimates of annual survival derived from post-season banding data only were consistently higher for adult females and juveniles of both sexes. We found patterns of seasonal survival varied by species, age, and to a lesser extent, sex. Hunter recovered birds exhibited similar spatial distributions regardless of banding season suggesting banded samples were from the same population. In contrast, goodness-of-fit tests suggest this assumption was statistically violated in some regions and years. We conclude that estimates of seasonal and annual survival for Black Ducks and Mallards based on the two-season banding program are valid and accurate based on model fit statistics, similarity in survival estimates across data and models, and similarities in the distribution of recoveries. The two-season program provides greater precision and insight into the survival process and will improve the ability of researchers and managers to test competing hypotheses regarding population regulation resulting in more effective management.
Collapse
Affiliation(s)
- Patrick K Devers
- Division of Migratory Bird Management, U.S. Fish and Wildlife Service, 11510 American Holly Drive, Laurel, Maryland, 20708, USA
| | - Robert L Emmet
- College of the Environment, University of Washington, Seattle, Washington, 98195, USA
| | - G Scott Boomer
- Division of Migratory Bird Management, U.S. Fish and Wildlife Service, 11510 American Holly Drive, Laurel, Maryland, 20708, USA
| | - Guthrie S Zimmerman
- Division of Migratory Bird Management, U.S. Fish and Wildlife Service, 3020 State University Drive East, Modoc Hall, Suite 2007, Sacramento, California, 95819, USA
| | - J Andrew Royle
- U.S. Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Road, Laurel, Maryland, 20708, USA
| |
Collapse
|
12
|
Mercado JE, Ortiz-Santana B, Kay SL. Endemic Jeffrey Pine Beetle Associates: Beetle/Mite Fungal Dissemination Strategies and Interactions That May Influence Beetle Population Levels. Microorganisms 2021; 9:1641. [PMID: 34442720 DOI: 10.3390/microorganisms9081641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/26/2021] [Accepted: 07/29/2021] [Indexed: 12/03/2022] Open
Abstract
Fungal and mite associates may drive changes in bark beetle populations, and mechanisms constraining beetle irruptions may be hidden in endemic populations. We characterized common fungi of endemic-level Jeffrey pine beetle (JPB) in western USA and analyzed their dissemination by JPB (maxillae and fecal pellet) and fungivorous mites to identify if endogenous regulation drove the population. We hypothesized that: (1) as in near-endemic mountain pine beetle populations, JPB’s mutualistic fungus would either be less abundant in endemic than in non-endemic populations or that another fungus may be more prevalent; (2) JPB primarily transports its mutualistic fungus, while its fungivorous mites primarily transport another fungus, and (3) based on the prevalence of yeasts in bark beetle symbioses, that a mutualistic interaction with blue-stain fungi present in that system may exist. Grosmannia clavigera was the most frequent JPB symbiont; however, the new here reported antagonist, Ophiostoma minus, was second in frequency. As hypothesized, JPB mostly carried its mutualist fungus while another fungus (i.e., antagonistic) was mainly carried by mites, but no fungal transport was obligate. Furthermore, we found a novel mutualistic interaction between the yeast Kuraishia molischiana and G. clavigera which fostered a growth advantage at temperatures associated with beetle colonization.
Collapse
|
13
|
Abstract
Although parasites are by definition costly to their host, demonstrating that a parasite is regulating its host abundance in the field can be difficult. Here we present an example of a gregarine parasite, Ascogregarina taiwanensis Lien and Levine (Apicomplexa: Lecudinidae), regulating its mosquito host, Aedes albopictus Skuse (Diptera: Culicidae), in Bermuda. We sampled larvae from container habitats over 2 yr, assessed parasite prevalence, and estimated host abundance from egg counts obtained in neighboring ovitraps. We regressed change in average egg count from 1 yr to the next on parasite prevalence and found a significant negative effect of parasite prevalence. We found no evidence of host density affecting parasite prevalence. Our results demonstrate that even for a parasite with moderate virulence, host regulation can occur in the field.
Collapse
Affiliation(s)
- John Soghigian
- Department of Biology, Clark University, Worcester, MA
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC
| | - Todd Livdahl
- Department of Biology, Clark University, Worcester, MA
| |
Collapse
|
14
|
Lundblad CG, Conway CJ. Ashmole's hypothesis and the latitudinal gradient in clutch size. Biol Rev Camb Philos Soc 2021; 96:1349-1366. [PMID: 33754488 DOI: 10.1111/brv.12705] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 02/22/2021] [Accepted: 02/24/2021] [Indexed: 11/27/2022]
Abstract
One enduring priority for ecologists has been to understand the cause(s) of variation in reproductive effort among species and localities. Avian clutch size generally increases with increasing latitude, both within and across species, but the mechanism(s) driving that pattern continue to generate hypotheses and debate. In 1961, a Ph.D. student at Oxford University, N. Philip Ashmole, proposed the influential hypothesis that clutch size varies in direct proportion to the seasonality of resources available to a population. Ashmole's hypothesis has been widely cited and discussed in the ecological literature. However, misinterpretation and confusion has been common regarding the mechanism that underlies Ashmole's hypothesis and the testable predictions it generates. We review the development of well-known hypotheses to explain clutch size variation with an emphasis on Ashmole's hypothesis. We then discuss and clarify sources of confusion about Ashmole's hypothesis in the literature, summarise existing evidence in support and refutation of the hypothesis, and suggest some under-utilised and novel approaches to test Ashmole's hypothesis and gain an improved understanding of the mechanisms responsible for variation in avian clutch size and fecundity, and life-history evolution in general.
Collapse
Affiliation(s)
- Carl G Lundblad
- Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Sciences, University of Idaho, 875 Perimeter Drive MS 1141, Moscow, ID, 83844, U.S.A
| | - Courtney J Conway
- U.S. Geological Survey, Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish & Wildlife Sciences, University of Idaho, 875 Perimeter Drive MS 1141, Moscow, ID, 83844, U.S.A
| |
Collapse
|
15
|
Tenan S, Becker D, Tolkmitt D, Schaub M. Decomposing fecundity and evaluating demographic influence of multiple broods in a migratory bird. J Anim Ecol 2021; 90:1071-1084. [PMID: 33496338 DOI: 10.1111/1365-2656.13432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 01/19/2021] [Indexed: 12/31/2022]
Abstract
Relevance of breeding season fecundity as a driver of population dynamics has been highlighted by many studies. Despite that, knowledge about how brood type specific (i.e. first, second or replacement) fecundity affects demography of multiple-brooded species is limited. In fact, estimation of brood type specific fecundity is often challenging due to imperfect detection of nesting attempts. We examined the demographic contribution and the feedback on population density of different components of fecundity, along with other vital rates, in a facultative multiple-brooded migratory bird. We used a novel formulation of a fecundity model that allows incorporating reproductive data for which information on the type of brood was unknown in some cases, and embedded it into an integrated population model (IPM) to obtain consensual estimates of all demographic rates, including brood type specific fecundities, reproductive success probabilities and proportion of breeding pairs that performed a second or replacement brood. We then conducted transient life table response experiments on IPM estimates to account for non-stationary environments. We applied the model to two 20-year datasets collected in a Swiss and a German local population of wrynecks Jynx torquilla. Brood type specific fecundities and temporal patterns of brood type specific probabilities of success, number of successful and unsuccessful first broods, probability of starting a second or a replacement brood and proportion of pairs that performed a second or a replacement brood differed between the two populations. However, changes in immigration rate and apparent survival were the dominant contributors to temporal variation and large sequential changes in realized population growth rates in both populations. In the Swiss population we also found that second brood fecundity declined when population size increased. Our study provides insight into the reproductive processes that affect population dynamics and mediate density-dependent fecundity in a migratory bird. In addition, the analytical approach proposed can be used in other studies of multiple-brooded species to maximize the use of available fecundity data through the estimation of unknown brood types, thus favouring a better understanding of the demographic contribution of brood type specific fecundity.
Collapse
Affiliation(s)
- Simone Tenan
- National Research Council, Institute of Marine Sciences (CNR-ISMAR), Venezia, Italy
| | | | | | - Michael Schaub
- Swiss Ornithological Institute, Sempach, Switzerland.,Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| |
Collapse
|
16
|
Cloyd RA. How Effective Is Conservation Biological Control in Regulating Insect Pest Populations in Organic Crop Production Systems? Insects 2020; 11:E744. [PMID: 33138249 DOI: 10.3390/insects11110744] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 10/22/2020] [Accepted: 10/27/2020] [Indexed: 11/27/2022]
Abstract
Simple Summary Organic crop production systems typically rely on conservation biological control to increase and sustain natural enemies including parasitoids and predators that will regulate insect pest populations below damaging levels. The use of flowering plants or floral resources to attract and retain natural enemies in organic crop production systems has not been consistent, based on the scientific literature, and most importantly, many studies do not correlate an increase in natural enemies with a reduction in plant damage. This may be associated with the effects of intraguild predation or the negative effects that can occur when multiple natural enemies are present in an ecosystem. Consequently, although incorporating flowering plants into organic crop production systems may increase the natural enemy assemblages, more robust scientific studies are warranted to determine the actual effects of natural enemies in reducing plant damage associated with insect pest populations. Abstract Organic crop production systems are designed to enhance or preserve the presence of natural enemies, including parasitoids and predators, by means of conservation biological control, which involves providing environments and habitats that sustain natural enemy assemblages. Conservation biological control can be accomplished by providing flowering plants (floral resources) that will attract and retain natural enemies. Natural enemies, in turn, will regulate existing insect pest populations to levels that minimize plant damage. However, evidence is not consistent, based on the scientific literature, that providing natural enemies with flowering plants will result in an abundance of natural enemies sufficient to regulate insect pest populations below economically damaging levels. The reason that conservation biological control has not been found to sufficiently regulate insect pest populations in organic crop production systems across the scientific literature is associated with complex interactions related to intraguild predation, the emission of plant volatiles, weed diversity, and climate and ecosystem resources across locations where studies have been conducted.
Collapse
|
17
|
Abstract
How genetic variation arises and persists over evolutionary time despite the depleting effects of natural selection remains a long-standing question. Here, we investigate the impacts of two extreme forms of population regulation-at the level of the total, mixed population (hard selection) and at the level of local, spatially distinct patches (soft selection)-on the emergence and fate of diversity under strong divergent selection. We find that while the form of population regulation has little effect on rates of diversification, it can modulate the long-term fate of genetic variation, diversity being more readily maintained under soft selection compared to hard selection. The mechanism responsible for coexistence is negative frequency-dependent selection which, while present initially under both forms of population regulation, persists over the long-term only under soft selection. Importantly, coexistence is robust to continued evolution of niche specialist types under soft selection but not hard selection. These results suggest that soft selection could be a general mechanism for the maintenance of ecological diversity over evolutionary time scales.
Collapse
Affiliation(s)
- Patrick Chen
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Rees Kassen
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| |
Collapse
|
18
|
Deffner D, McElreath R. The importance of life history and population regulation for the evolution of social learning. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190492. [PMID: 32475333 PMCID: PMC7293155 DOI: 10.1098/rstb.2019.0492] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2020] [Indexed: 02/05/2023] Open
Abstract
Social learning and life history interact in human adaptation, but nearly all models of the evolution of social learning omit age structure and population regulation. Further progress is hindered by a poor appreciation of how life history affects selection on learning. We discuss why life history and age structure are important for social learning and present an exemplary model of the evolution of social learning in which demographic properties of the population arise endogenously from assumptions about per capita vital rates and different forms of population regulation. We find that, counterintuitively, a stronger reliance on social learning is favoured in organisms characterized by 'fast' life histories with high mortality and fertility rates compared to 'slower' life histories typical of primates. Long lifespans make early investment in learning more profitable and increase the probability that the environment switches within generations. Both effects favour more individual learning. Additionally, under fertility regulation (as opposed to mortality regulation), more juveniles are born shortly after switches in the environment when many adults are not adapted, creating selection for more individual learning. To explain the empirical association between social learning and long life spans and to appreciate the implications for human evolution, we need further modelling frameworks allowing strategic learning and cumulative culture. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.
Collapse
Affiliation(s)
- Dominik Deffner
- Max Planck Institute for Evolutionary Anthropology, Department of Human Behavior, Ecology and Culture, Leipzig, Germany
| | | |
Collapse
|
19
|
Abstract
The regulation of population density is suggested to be indirect and occurs with a time-lag effect, as well as being female centred. Herein, we present a quantitative analysis on the precise, timely and male-dominated self-regulation of Chinese alligator (Alligator sinensis) populations. Analysis of 31 years of data revealed gender differences in regulation patterns. Population dynamics were restricted by male density rather than population density, and population growth was halted (birth rate = 0) when male density exceeded 83.14 individuals per hectare, until some males were removed, especially adult males. This rapid and accurate response supports the notions of intrinsic mechanisms and population-wide regulation response. Furthermore, density stress affected mating success rather than parental care to juveniles, i.e. females avoided unnecessary reproduction costs, which may represent an evolutionary advantage. Our findings highlighted the importance of further studies on related physiological mechanisms that focus on four characteristics: quantity breeds quality, gender differences, male density thresholds and nonlinearity.
Collapse
Affiliation(s)
- Lan Zhao
- 1 MOE Key Laboratory of Biosystems Homeostasis and Protection, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University , Hangzhou 310058 , People's Republic of China
| | - Li-Ming Fang
- 2 Changxing Chinese Alligator Nature Reserve , Changxing 313100 , People's Republic of China
| | - Qiu-Hong Wan
- 1 MOE Key Laboratory of Biosystems Homeostasis and Protection, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University , Hangzhou 310058 , People's Republic of China
| | - Sheng-Guo Fang
- 1 MOE Key Laboratory of Biosystems Homeostasis and Protection, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University , Hangzhou 310058 , People's Republic of China
| |
Collapse
|
20
|
Wright J, Solbu EB, Engen S. Contrasting patterns of density-dependent selection at different life stages can create more than one fast-slow axis of life-history variation. Ecol Evol 2020; 10:3068-3078. [PMID: 32211177 PMCID: PMC7083673 DOI: 10.1002/ece3.6122] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 01/28/2020] [Accepted: 02/04/2020] [Indexed: 11/24/2022] Open
Abstract
There has been much recent research interest in the existence of a major axis of life-history variation along a fast-slow continuum within almost all major taxonomic groups. Eco-evolutionary models of density-dependent selection provide a general explanation for such observations of interspecific variation in the "pace of life." One issue, however, is that some large-bodied long-lived "slow" species (e.g., trees and large fish) often show an explosive "fast" type of reproduction with many small offspring, and species with "fast" adult life stages can have comparatively "slow" offspring life stages (e.g., mayflies). We attempt to explain such life-history evolution using the same eco-evolutionary modeling approach but with two life stages, separating adult reproductive strategies from offspring survival strategies. When the population dynamics in the two life stages are closely linked and affect each other, density-dependent selection occurs in parallel on both reproduction and survival, producing the usual one-dimensional fast-slow continuum (e.g., houseflies to blue whales). However, strong density dependence at either the adult reproduction or offspring survival life stage creates quasi-independent population dynamics, allowing fast-type reproduction alongside slow-type survival (e.g., trees and large fish), or the perhaps rarer slow-type reproduction alongside fast-type survival (e.g., mayflies-short-lived adults producing few long-lived offspring). Therefore, most types of species life histories in nature can potentially be explained via the eco-evolutionary consequences of density-dependent selection given the possible separation of demographic effects at different life stages.
Collapse
Affiliation(s)
- Jonathan Wright
- Department of BiologyCentre for Biodiversity DynamicsNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Erik Blystad Solbu
- Department of BiologyCentre for Biodiversity DynamicsNorwegian University of Science and Technology (NTNU)TrondheimNorway
- Department of Landscape and BiodiversityNorwegian Institute of Bioeconomy Research (NIBIO)TrondheimNorway
| | - Steinar Engen
- Department of MathematicsCentre for Biodiversity DynamicsNorwegian University of Science and Technology (NTNU)TrondheimNorway
| |
Collapse
|
21
|
Southwell C, Emmerson L. Density dependence forces divergent population growth rates and alters occupancy patterns of a central place foraging Antarctic seabird. Ecol Evol 2020; 10:2339-2351. [PMID: 32184985 PMCID: PMC7069296 DOI: 10.1002/ece3.6037] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/27/2019] [Accepted: 01/03/2020] [Indexed: 11/11/2022] Open
Abstract
Density-dependent regulation is an important process in spatio-temporal population dynamics because it can alter the effects of synchronizing processes operating over large spatial scales. Most frequently, populations are regulated by density dependence when higher density leads to reduced individual fitness and population growth, but inverse density dependence can also occur when small populations are subject to higher extinction risks. We investigate whether density-dependent regulation influences population growth for the Antarctic breeding Adélie penguin Pygoscelis adeliae. Understanding the prevalence and nature of density dependence for this species is important because it is considered a sentinel species reflecting the impacts of fisheries and environmental change over large spatial scales in the Southern Ocean, but the presence of density dependence could introduce uncertainty in this role. Using data on population growth and indices of resource availability for seven regional Adélie penguin populations located along the East Antarctic coastline, we find compelling evidence that population growth is constrained at some locations by the amount of breeding habitat available to individuals. Locations with low breeding habitat availability had reduced population growth rates, higher overall occupancy rates, and higher occupancy of steeper slopes that are sparsely occupied or avoided at other locations. Our results are consistent with evolutionary models of avian breeding habitat selection where individuals search for high-quality nest sites to maximize fitness returns and subsequently occupy poorer habitat as population density increases. Alternate explanations invoking competition for food were not supported by the available evidence, but strong conclusions on food-related density dependence were constrained by the paucity of food availability data over the large spatial scales of this region. Our study highlights the importance of incorporating nonconstant conditions of species-environment relationships into predictive models of species distributions and population dynamics, and provides guidance for improved monitoring of fisheries and climate change impacts in the Southern Ocean.
Collapse
Affiliation(s)
- Colin Southwell
- Australian Antarctic DivisionDepartment of the Environment and EnergyKingstonTas.Australia
| | - Louise Emmerson
- Australian Antarctic DivisionDepartment of the Environment and EnergyKingstonTas.Australia
| |
Collapse
|
22
|
Thibaut LM, Connolly SR. Hierarchical modeling strengthens evidence for density dependence in observational time series of population dynamics. Ecology 2019; 101:e02893. [PMID: 31529700 DOI: 10.1002/ecy.2893] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 07/01/2019] [Accepted: 07/18/2019] [Indexed: 11/09/2022]
Abstract
The extent to which populations in nature are regulated by density-dependent processes is unresolved. While experiments increasingly find evidence of strong density dependence, unmanipulated population time series yield much more ambiguous evidence of regulation, especially when accounting for effects of observation error. Here, we reexamine the evidence for density dependence in time series of population sizes in nature, by conducting an aggregate analysis of the populations in the Global Population Dynamics Database (GPDD). First, following the conventional approach, we fit a density-dependent and a density-independent variant of the Gompertz state-space model to each time series. Then, we conduct an aggregate analysis of the entire database by considering two random-effects density-dependent models that leverage information across data sets. When individual time series are tested independently, we find very little evidence for density dependence. However, in the aggregate, we find very strong evidence for density dependence, even though, paradoxically, estimated strengths of density dependence for individual time series tend to be weaker than when each individual time series is analyzed independently. Furthermore, a hierarchical model that accounts for taxonomic variation in the strength of density dependence reveals that density dependence is consistently stronger in insects and fish than in birds and mammals. Our findings resolve apparent inconsistencies between observational and experimental studies of density dependence by revealing that the observational record does indeed contain strong support for the hypothesis that density dependence is widespread in nature.
Collapse
Affiliation(s)
- Loïc M Thibaut
- College of Marine and Environmental Sciences, ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia.,School of Mathematics and Statistics, The University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Sean R Connolly
- College of Marine and Environmental Sciences, ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia
| |
Collapse
|
23
|
Vrtílek M, Žák J, Polačik M, Blažek R, Reichard M. Rapid growth and large body size in annual fish populations are compromised by density-dependent regulation. J Fish Biol 2019; 95:673-678. [PMID: 31102276 DOI: 10.1111/jfb.14052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 05/17/2019] [Indexed: 06/09/2023]
Abstract
We tested the effect of population density on maximum body size in three sympatric species of annual killifishes Nothobranchius spp. from African ephemeral pools. We found a clear negative effect of population density on body size, limiting their capacity for extremely fast development and rapid growth. This suggests that density-dependent population regulation and the ephemeral character of their habitat impose contrasting selective pressures on the life history of annual killifishes.
Collapse
Affiliation(s)
- Milan Vrtílek
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
| | - Jakub Žák
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
- Department of Zoology, Faculty of Sciences, Charles University, Praha, Czech Republic
| | - Matej Polačik
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
| | - Radim Blažek
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
| | - Martin Reichard
- The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
| |
Collapse
|
24
|
Møller AP, Laursen K. The ecological significance of extremely large flocks of birds. Ecol Evol 2019; 9:6559-6567. [PMID: 31236244 PMCID: PMC6580271 DOI: 10.1002/ece3.5234] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/09/2019] [Accepted: 04/18/2019] [Indexed: 11/29/2022] Open
Abstract
Population size is generally limited by resource availability during and outside the breeding season. Therefore, maximum size of flocks may provide important information on population regulation and the influence of diet and trophic level on maximal degree of sociality. We hypothesized that (a) flock size should increase with nutrient availability; (b) flock size should decrease with latitude because productivity is higher at lower latitude; (c) aquatic habitats should have larger flocks than terrestrial habitats because the former are less accessible; (d) smaller species should have larger flocks because they require overall less food; (e) human-impacted species that live in perturbed habitats should have smaller flocks than other species; (f) flock size should decrease with increasing trophic level because there is a reduction in biomass due to conversion at each trophic level; and (g) flocks of species depending on ancestral landscapes should have decreased in size in recent years due to human impact (e.g., land-use). We obtained 1564 observations of flocks that exceeded 100,000 individuals in order to test the predictions listed above. Most effect sizes were small to medium accounting for 1%-9% of the variance, while large effects accounting for 25% or more were only found for total nitrogen used per km2 and area used for agriculture. Changes in large bird flocks were caused by habitat degradation and persecution, and temporal decline in size of large flocks revealed changes in nutrient use, reductions in nutrient cycling, and changes in flock size linked to trophic level.
Collapse
Affiliation(s)
- Anders Pape Møller
- Ecologie Systématique Evolution, Université Paris‐Sud, CNRS, AgroParisTechUniversité Paris‐SaclayOrsay CedexFrance
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life SciencesBeijing Normal UniversityBeijingChina
| | | |
Collapse
|
25
|
Abstract
Aphid invasions of North American cereal crops generally have started with colonization of a new region or crop, followed by range expansion and outbreaks that vary in frequency and scale owing to geographically variable influences. To improve understanding of this process and management, we compare the invasion ecology of and management response to three cereal aphids: sugarcane aphid, Russian wheat aphid, and greenbug. The region exploited is determined primarily by climate and host plant availability. Once an area is permanently or annually colonized, outbreak intensity is also affected by natural enemies and managed inputs, such as aphid-resistant cultivars and insecticides. Over time, increases in natural enemy abundance and diversity, improved compatibility among management tactics, and limited threshold-based insecticide use have likely increased resilience of aphid regulation. Application of pest management foundational practices followed by a focus on compatible strategies are relevant worldwide. Area-wide pest management is most appropriate to large-scale cereal production systems, as exemplified in the Great Plains of North America.
Collapse
Affiliation(s)
- Michael J Brewer
- Texas A&M AgriLife Research and Department of Entomology, Texas A&M University, Corpus Christi, Texas 78406, USA;
| | - Frank B Peairs
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523, USA;
| | - Norman C Elliott
- Wheat, Peanut, and Other Field Crops Research Unit, USDA-ARS, Stillwater, Oklahoma 74075, USA;
| |
Collapse
|
26
|
Li G, Li J, Kohl KD, Yin B, Wei W, Wan X, Zhu B, Zhang Z. Dietary shifts influenced by livestock grazing shape the gut microbiota composition and co-occurrence networks in a local rodent species. J Anim Ecol 2018; 88:302-314. [PMID: 30381827 DOI: 10.1111/1365-2656.12920] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 10/12/2018] [Accepted: 10/14/2018] [Indexed: 12/31/2022]
Abstract
The collapse of large wild herbivores with replacement of livestock is causing global plant community and diversity shifts, resulting in altered food availability and diet composition of other sympatric small herbivores in grasslands. How diet shifts affect the gut microbiota of small mammals and whether these changes may translate into complex interactions among coexisting herbivores remain largely unknown. We conducted both a field experiment and a laboratory diet manipulation experiment to test whether sheep grazing induces a diet shift and thus alters the gut microbiota of a small rodent species living in grassland. We found that enclosures subjected to grazing were mostly dominated by Stipa krylovii (accounting for 53.6% of the total biomass) and that voles consumed significantly more S. krylovii and less Cleistogenes squarrosa in grazed enclosures. Voles in grazing enclosures exhibited significantly lower abundances of Firmicutes, higher abundances of Bacteroidetes and significantly lower measurements of alpha diversity. The microbiota from voles in the grazed enclosures had a smaller and more simplified co-occurrence network with relatively higher percentage of positive interactions. Analysis based on dietary clusters indicated that grazing-induced changes in diet composition contributed to the distinct gut microbial community of voles in enclosures. We verified our findings using laboratory experiments, in which voles were exclusively fed C. squarrosa (high carbohydrate, high fibre and high in secondary compounds), S. krylovii (low carbohydrate, low fibre and low in secondary compounds) or Leymus chinensis (nutritionally intermediate). We observed that the gut microbiota of voles changed with the three different diets, supporting the idea that the effects of sheep grazing on the gut microbiota of Brandt's voles may be related to grazing-induced diet shifts. Our results highlighted the negative effects of livestock grazing on small mammals in grassland via changes in plant community and gut microbiota of small mammals and help to better understand the cascading consequences of realistic scenarios of world-wide decline in large wild herbivores.
Collapse
Affiliation(s)
- Guoliang Li
- State Key Laboratory of Integrated Pest Management, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Jing Li
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Kevin D Kohl
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Baofa Yin
- Colleges of Bioscience and Biotechnology, Yangzhou University, Yangzhou, China
| | - Wanhong Wei
- Colleges of Bioscience and Biotechnology, Yangzhou University, Yangzhou, China
| | - Xinrong Wan
- State Key Laboratory of Integrated Pest Management, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Baoli Zhu
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Zhibin Zhang
- State Key Laboratory of Integrated Pest Management, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
27
|
Lancaster J, Downes BJ. Aquatic versus Terrestrial Insects: Real or Presumed Differences in Population Dynamics? Insects 2018; 9:insects9040157. [PMID: 30388810 PMCID: PMC6315690 DOI: 10.3390/insects9040157] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 10/29/2018] [Accepted: 10/30/2018] [Indexed: 01/28/2023]
Abstract
The study of insect populations is dominated by research on terrestrial insects. Are aquatic insect populations different or are they just presumed to be different? We explore the evidence across several topics. (1) Populations of terrestrial herbivorous insects are constrained most often by enemies, whereas aquatic herbivorous insects are constrained more by food supplies, a real difference related to the different plants that dominate in each ecosystem. (2) Population outbreaks are presumed not to occur in aquatic insects. We report three examples of cyclical patterns; there may be more. (3) Aquatic insects, like terrestrial insects, show strong oviposition site selection even though they oviposit on surfaces that are not necessarily food for their larvae. A novel outcome is that density of oviposition habitat can determine larval densities. (4) Aquatic habitats are often largely 1-dimensional shapes and this is presumed to influence dispersal. In rivers, drift by insects is presumed to create downstream dispersal that has to be countered by upstream flight by adults. This idea has persisted for decades but supporting evidence is scarce. Few researchers are currently working on the dynamics of aquatic insect populations; there is scope for many more studies and potentially enlightening contrasts with terrestrial insects.
Collapse
Affiliation(s)
- Jill Lancaster
- School of Geography, University of Melbourne, Melbourne, VIC 3010, Australia.
| | - Barbara J Downes
- School of Geography, University of Melbourne, Melbourne, VIC 3010, Australia.
| |
Collapse
|
28
|
Møller AP, Thorup O, Laursen K. Predation and nutrients drive population declines in breeding waders. Ecol Appl 2018; 28:1292-1301. [PMID: 29679425 DOI: 10.1002/eap.1729] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 02/15/2018] [Accepted: 03/16/2018] [Indexed: 06/08/2023]
Abstract
Allee effects are defined as a decline in per capita fitness at low population density. We hypothesized that predation reduces population size of breeding waders and thereby the efficiency of predator deterrence, while total nitrogen through its effects on primary and secondary productivity increases population size. Therefore, nest predation could have negative consequences for population size because nest failure generally results in breeding dispersal and hence reduced local population density. To test these predictions, we recorded nest predation in five species of waders for 4,745 nests during 1987-2015 at the nature reserve Tipperne, Denmark. Predation rates were generally negatively related to conspecific and heterospecific population density, but positively related to overall population density of the entire wader community. Nest predation and population density were related to ground water level, management (grazing and mowing), and nutrients. High nest predation with a time lag of one year resulted in low overall breeding population density, while high nutrient levels resulted in higher population density. These two factors accounted for 86% of the variance in population size, presumably due to effects of nest predation on emigration, while nutrient levels increased the level of vegetation cover and the abundance of food in the surrounding brackish water. These findings are consistent with the hypothesis that predation may reduce population density through negative density dependence, while total nitrogen at adjacent shallow water may increase population size. Nest predation rates were reduced by high ground water level in March, grazing by cattle and mowing that affected access to and susceptibility of nests to predators. These effects can be managed to benefit breeding waders.
Collapse
Affiliation(s)
- Anders Pape Møller
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, F-91405, Orsay Cedex, France
| | - Ole Thorup
- Amphi Consult, V. Vedsted Byvej 32, DK-6760, Ribe, Denmark
| | - Karsten Laursen
- Department of Bioscience, Aarhus University, Grenåvej 14, DK-8410, Aarhus, Denmark
| |
Collapse
|
29
|
Zimmermann F, Ricard D, Heino M. Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth. J Anim Ecol 2018; 87:672-681. [PMID: 29380364 DOI: 10.1111/1365-2656.12800] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 12/09/2017] [Indexed: 11/27/2022]
Abstract
Population regulation is a central concept in ecology, yet in many cases its presence and the underlying mechanisms are difficult to demonstrate. The current paradigm maintains that marine fish populations are predominantly regulated by density-dependent recruitment. While it is known that density-dependent somatic growth can be present too, its general importance remains unknown and most practical applications neglect it. This study aimed to close this gap by for the first time quantifying and comparing density dependence in growth and recruitment over a large set of fish populations. We fitted density-dependent models to time-series data on population size, recruitment and age-specific weight from commercially exploited fish populations in the Northeast Atlantic Ocean and the Baltic Sea. Data were standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. Statistically significant density dependence in recruitment was detected in a large proportion of populations (70%), whereas for density dependence in somatic growth the prevalence of density dependence depended heavily on the method (26% and 69%). Despite age-dependent variability, the density dependence in recruitment was consistently stronger among age groups and between alternative approaches that use weight-at-age or weight increments to assess growth. Estimates of density-dependent reduction in biomass underlined these results: 97% of populations with statistically significant parameters for growth and recruitment showed a larger impact of density-dependent recruitment on population biomass. The results reaffirm the importance of density-dependent recruitment in marine fishes, yet they also show that density dependence in somatic growth is not uncommon. Furthermore, the results are important from an applied perspective because density dependence in somatic growth affects productivity and catch composition, and therefore the benefits of maintaining fish populations at specific densities.
Collapse
Affiliation(s)
- Fabian Zimmermann
- Institute of Marine Research, Bergen, Norway.,Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Daniel Ricard
- Biology Centre AS CR, v.v.i., Institute of Hydrobiology, České Budĕjovice, Czech Republic.,Fisheries and Oceans Canada, Gulf Fisheries Centre, Moncton, NB, Canada
| | - Mikko Heino
- Institute of Marine Research, Bergen, Norway.,Department of Biological Sciences, University of Bergen, Bergen, Norway.,International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.,Institute of Oceanography, National Taiwan University, Taipei, Taiwan
| |
Collapse
|
30
|
Johnson PTJ, Wilber MQ. Biological and statistical processes jointly drive population aggregation: using host-parasite interactions to understand Taylor's power law. Proc Biol Sci 2018; 284:rspb.2017.1388. [PMID: 28931738 DOI: 10.1098/rspb.2017.1388] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/10/2017] [Indexed: 12/25/2022] Open
Abstract
The macroecological pattern known as Taylor's power law (TPL) represents the pervasive tendency of the variance in population density to increase as a power function of the mean. Despite empirical illustrations in systems ranging from viruses to vertebrates, the biological significance of this relationship continues to be debated. Here we combined collection of a unique dataset involving 11 987 amphibian hosts and 332 684 trematode parasites with experimental measurements of core epidemiological outcomes to explicitly test the contributions of hypothesized biological processes in driving aggregation. After using feasible set theory to account for mechanisms acting indirectly on aggregation and statistical constraints inherent to the data, we detected strongly consistent influences of host and parasite species identity over 7 years of sampling. Incorporation of field-based measurements of host body size, its variance and spatial heterogeneity in host density accounted for host identity effects, while experimental quantification of infection competence (and especially virulence from the 20 most common host-parasite combinations) revealed the role of species-by-environment interactions. By uniting constraint-based theory, controlled experiments and community-based field surveys, we illustrate the joint influences of biological and statistical processes on parasite aggregation and emphasize their importance for understanding population regulation and ecological stability across a range of systems, both infectious and free-living.
Collapse
Affiliation(s)
- Pieter T J Johnson
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Mark Q Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| |
Collapse
|
31
|
Sanad M, Sun JS, Shamseldean MSM, Wang Y, Gaugler R. Superparasitism and Population Regulation of the Mosquito-Parasitic Mermithid Nematodes Romanomermis iyengari and Strelkovimermis spiculatus. J Nematol 2017; 49:316-320. [PMID: 29062155 PMCID: PMC5644925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Indexed: 06/07/2023] Open
Abstract
Superparasitism is a common phenomenon in mosquito-parasitic mermithid nematodes. Multiple nematodes are needed in a single host to produce males. Host selection behavior and intraspecific competition among Romanomermis iyengari and Strelkovimermis spiculatus were investigated against their host, Culex pipiens pipiens in laboratory experiments. In a choice assay between previously infected and uninfected host larvae, infectious preparasites of both nematode species could distinguish not only between infected and uninfected hosts, but even between different parasite loads in showing a strong preference for uninfected hosts or hosts with a low parasite load. Host heart rate declined briefly immediately after parasitism. Superparasitism resulted in increased parasite mortality. Scramble competition within mosquito larvae for limited host nutrients, coupled with a skewed sex ratio favoring males, is assumed to lead to parasite population decline and subsequently toward host-parasite population equilibrium. The ability of mermithid preparasites to accurately assess parasite load likely plays an important role in host population dynamics and regulation.
Collapse
Affiliation(s)
- Manar Sanad
- Department of Zoology and Agricultural Nematology, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
- Center for Vector Biology, Rutgers University, New Brunswick, NJ 08901-8536
| | - Jennifer S Sun
- Center for Vector Biology, Rutgers University, New Brunswick, NJ 08901-8536
| | - Muhammad S M Shamseldean
- Department of Zoology and Agricultural Nematology, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
| | - Yi Wang
- Center for Vector Biology, Rutgers University, New Brunswick, NJ 08901-8536
| | - Randy Gaugler
- Center for Vector Biology, Rutgers University, New Brunswick, NJ 08901-8536
| |
Collapse
|
32
|
Ferguson JM, Reichert BE, Fletcher RJ, Jager HI. Detecting population-environmental interactions with mismatched time series data. Ecology 2017; 98:2813-2822. [PMID: 28759123 DOI: 10.1002/ecy.1966] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 06/14/2017] [Accepted: 07/10/2017] [Indexed: 11/08/2022]
Abstract
Time series analysis is an essential method for decomposing the influences of density and exogenous factors such as weather and climate on population regulation. However, there has been little work focused on understanding how well commonly collected data can reconstruct the effects of environmental factors on population dynamics. We show that, analogous to similar scale issues in spatial data analysis, coarsely sampled temporal data can fail to detect covariate effects when interactions occur on timescales that are fast relative to the survey period. We propose a method for modeling mismatched time series data that couples high-resolution environmental data to low-resolution abundance data. We illustrate our approach with simulations and by applying it to Florida's southern Snail kite population. Our simulation results show that our method can reliably detect linear environmental effects and that detecting nonlinear effects requires high-resolution covariate data even when the population turnover rate is slow. In the Snail kite analysis, our approach performed among the best in a suite of previously used environmental covariates explaining Snail kite dynamics and was able to detect a potential phenological shift in the environmental dependence of Snail kites. Our work provides a statistical framework for reliably detecting population-environment interactions from coarsely surveyed time series. An important implication of this work is that the low predictability of animal population growth by weather variables found in previous studies may be due, in part, to how these data are utilized as covariates.
Collapse
Affiliation(s)
- Jake M Ferguson
- National Institute of Mathematical and Biology Synthesis, University of Tennessee, Knoxville, Tennessee, 37996, USA.,Center for Modeling Complex Interactions, University of Idaho, 875 Perimeter Drive, Moscow, Idaho, 83844, USA
| | - Brian E Reichert
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, 32611, USA
| | - Robert J Fletcher
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, 32611, USA
| | - Henriëtte I Jager
- Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee, 37830, USA
| |
Collapse
|
33
|
Gall CA, Rose RK, Hurd LE. Cohabiting With the Enemy: Comparative Population Ecology of Two Mantid Species in a Successional Old Field. Environ Entomol 2017; 46:766-770. [PMID: 28881948 PMCID: PMC6279115 DOI: 10.1093/ee/nvx110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Indexed: 06/07/2023]
Abstract
Two praying mantids, Tenodera aridifolia sinensis Saussure and Tenodera angustipennis Saussure, are commonly found in the same old-field habitats in the eastern United States and in much of temperate zone Asia. Naturally established populations of these two species were studied intensively over two consecutive years (2010 and 2011) in an old field in southeastern Virginia, to compare life history features relevant to how they coexist, or whether one or the other of them is likely to be more successful in the same habitat. Populations of both species declined about 50% from 2010 to 2011 (adults from 47 to 21 for T. a. sinensis; 37 to 20 for T. angustipennis), but T. a. sinensis oviposited 10 oothecae and T. angustipennis only one in 2011. Tenodera a. sinensis was more abundant in the study site in both years, hatched earlier, and matured and oviposited earlier than T. angustipennis. Fewer females of both species survived to maturity in 2011 than in 2010, possibly indicating a reduction in prey or habitat suitability in 2011. We suggest that T. angustipennis will always be at a disadvantage as a result of its smaller body size, because of interspecific predation (and potentially competition) from its congener, lower clutch size, and susceptibility to egg parasitism. Further, environmental variability across field habitats and years profoundly affects populations of both species in successional old fields.
Collapse
Affiliation(s)
- Cory A. Gall
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529 (; )
- Current address: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164
| | - Robert K. Rose
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529 (; )
| | - Lawrence E. Hurd
- Department of Biology, Washington and Lee University, Lexington, VA 24450 ()
| |
Collapse
|
34
|
Woodworth BK, Wheelwright NT, Newman AEM, Norris DR. Local density regulates migratory songbird reproductive success through effects on double-brooding and nest predation. Ecology 2017; 98:2039-2048. [PMID: 28555872 DOI: 10.1002/ecy.1911] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 05/09/2017] [Accepted: 05/16/2017] [Indexed: 12/29/2022]
Abstract
Knowledge of the density-dependent processes that regulate animal populations is key to understanding, predicting, and conserving populations. In migratory birds, density-dependence is most often studied during the breeding season, yet we still lack a robust understanding of the reproductive traits through which density influences individual reproductive success. We used 27-yr of detailed, individual-level productivity data from an island-breeding population of Savannah sparrows Passerculus sandwichensis to evaluate effects of local and total annual population density on female reproductive success. Local density (number of neighbors within 50 m of a female's nest) had stronger effects on the number of young fledged than did total annual population density. Females nesting in areas of high local density were more likely to suffer nest predation and less likely to initiate and fledge a second clutch, which led to fewer young fledged in a season. Fledging fewer young subsequently decreased the likelihood of a female recruiting offspring into the breeding population in a subsequent year. Collectively, these results provide insight into the scale and reproductive mechanisms mediating density-dependent reproductive success and fitness in songbirds.
Collapse
Affiliation(s)
- Bradley K Woodworth
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | | | - Amy E M Newman
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - D Ryan Norris
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| |
Collapse
|
35
|
Tenan S, Fasola M, Volponi S, Tavecchia G. Conspecific and not performance-based attraction on immigrants drives colony growth in a waterbird. J Anim Ecol 2017; 86:1074-1081. [PMID: 28502084 DOI: 10.1111/1365-2656.12690] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Local recruitment and immigration play an important part in the dynamics and growth of animal populations. However, their estimation and incorporation into open population models is, in most cases, problematic. We studied factors affecting the growth of a recently established colony of Eurasian spoonbill (Platalea leucorodia) and assessed the contribution of local recruits, i.e. birds born in the colony, and immigrants, i.e. birds of unknown origin, to colony growth. We applied an integrated population model that accounts for uncertainty in breeding state assignment and merges population surveys, local fecundity and individual longitudinal data of breeding and non-breeding birds, to estimate demographic rates and the relative role of recruitment and immigration in driving the local dynamics. We also used this analytical framework to assess the degree of support for the 'performance-based' and 'conspecific attraction' hypotheses as possible mechanisms of colony growth. Among the demographic rates, only immigration was positively and significantly correlated with population growth rate. In addition, the number of immigrants settling in the colony was positively correlated with colony size in the previous and current year, but was not correlated with fecundity of the previous year. Our results suggest that the variation in immigration affected colony dynamics and that conspecific attraction likely triggered the relevant role of immigration in the growth of a recently formed waterbird colony, supporting the need of including immigration in population analysis.
Collapse
Affiliation(s)
- Simone Tenan
- Vertebrate Zoology Section, MUSE - Museo delle Scienze, Trento, Italy
| | - Mauro Fasola
- Dipartimento Scienze della Terra e dell'Ambiente, Università di Pavia, Pavia, Italy
| | - Stefano Volponi
- Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), Ozzano Emilia (BO), Italy
| | - Giacomo Tavecchia
- Population Ecology Group, IMEDEA (CSIC-UIB), Esporles (Mallorca), Spain
| |
Collapse
|
36
|
Fauteux D, Gauthier G, Berteaux D. Top-down limitation of lemmings revealed by experimental reduction of predators. Ecology 2017; 97:3231-3241. [PMID: 27870031 DOI: 10.1002/ecy.1570] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 05/31/2016] [Accepted: 07/06/2016] [Indexed: 11/07/2022]
Abstract
It is generally recognized that delayed density-dependence is responsible for cyclic population dynamics. However, it is still uncertain whether a single factor can explain why some rodent populations fluctuate according to a 3-4 yr periodicity. There is increasing evidence that predation may play a role in lemming population cycles, although this effect may vary seasonally. To address this issue, we conducted an experiment where we built a large exclosure (9 ha) to protect brown lemmings (Lemmus trimucronatus) from avian and terrestrial predators. We tested the hypothesis that predation is a limiting factor for lemmings by measuring the demographic consequences of a predator reduction during the growth and peak phases of the cycle. We assessed summer (capture-mark-recapture methods) and winter (winter nest sampling) lemming demography on two grids located on Bylot Island, Nunavut, Canada from 2008 to 2015. The predator exclosure became fully effective in July 2013, allowing us to compare demography between the control and experimental grids before and during the treatment. Lemming abundance, survival and proportion of juveniles were similar between the two grids before the treatment. During the predator-reduction period, summer densities were on average 1.9× higher inside the experimental grid than the control and this effect was greatest for adult females and juveniles (densities 2.4× and 3.4× higher, respectively). Summer survival was 1.6× higher on the experimental grid than the control whereas body mass and proportion of juveniles were also slightly higher. Winter nest densities remained high inside the predator reduction grid following high summer abundance, but declined on the control grid. These results confirm that predation limits lemming population growth during the summer due to its negative impact on survival. However, it is possible that in winter, predation may interact with other factors affecting reproduction and ultimately population cycles.
Collapse
Affiliation(s)
- Dominique Fauteux
- Department of Biology and Centre d'Études Nordiques, Université Laval, 1045 Avenue de la Médecine, Québec, Québec, G1V 0A6, Canada
| | - Gilles Gauthier
- Department of Biology and Centre d'Études Nordiques, Université Laval, 1045 Avenue de la Médecine, Québec, Québec, G1V 0A6, Canada
| | - Dominique Berteaux
- Canada Research Chair on Northern Biodiversity and Centre d'Études Nordiques, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada
| |
Collapse
|
37
|
Weinstein S, Titcomb G, Agwanda B, Riginos C, Young H. Parasite responses to large mammal loss in an African savanna. Ecology 2017; 98:1839-1848. [PMID: 28403506 DOI: 10.1002/ecy.1858] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 03/01/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022]
Abstract
Biodiversity loss can alter disease transmission; however, the magnitude and direction of these effects vary widely across ecosystems, scales, and pathogens. Here we experimentally examine the effects of one of the most globally pervasive patterns of biodiversity decline, the selective loss of large wildlife, on infection probability, intensity and population size of a group of common rodent-borne parasites - macroparasitic helminths. Consistent with previous work on vector-borne pathogens, we found that large wildlife removal causes strong and systematic increases of rodent-borne parasites, largely due to increases in rodent density, as rodents are released from competition with larger herbivores. Although we predicted that increased host density would also increase per capita infection among all directly transmitted parasites, this additional amplification occurred for only two of three examined parasites. Furthermore, the actual effects of large mammal loss on per capita infection were mediated by the complex suite of abiotic and biotic factors that regulate parasite transmission. Thus, while these results strongly suggest that large wildlife loss will cause systematic increases in rodent parasite populations, they also underscore the difficulty of making more specific predictions for a given parasite based on simple attributes such as transmission mode or life history strategy. Instead, detailed information on the ecology of each parasite species would be necessary to make more accurate predictions of how biodiversity loss will affect infection.
Collapse
Affiliation(s)
- Sara Weinstein
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA
| | - Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
| | - Bernard Agwanda
- Zoology Department, Mammalogy Section, National Museums Kenya, Nairobi, Kenya
| | - Corinna Riginos
- Mpala Research Centre, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Hillary Young
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
| |
Collapse
|
38
|
Abstract
Carrying capacity is 1 driver of wildlife population dynamics. Although in previous studies carrying capacity was considered to be a fixed entity, it may differ among locations due to environmental variation. The factors underlying variability in carrying capacity, however, have rarely been examined. Here, we investigated spatial heterogeneity in the carrying capacity of Japanese sika deer (
Cervus nippon
) from 2005 to 2014 in Yamanashi Prefecture, central Japan (mesh with grid cells of 5.5×4.6 km) by state-space modeling. Both carrying capacity and density dependence differed greatly among cells. Estimated carrying capacities ranged from 1.34 to 98.4 deer/km
2
. According to estimated population dynamics, grid cells with larger proportions of artificial grassland and deciduous forest were subject to lower density dependence and higher carrying capacity. We conclude that population dynamics of ungulates may vary spatially through spatial variation in carrying capacity and that the density level for controlling ungulate abundance should be based on the current density level relative to the carrying capacity for each area.
Collapse
Affiliation(s)
- Hayato Iijima
- Yamanashi Forest Research Institute , 2290-1, Saishoji, Fujikawa, Yamanashi 400-0502 , Japan (HI).,Eastern Field Station, Institute of Environmental Sciences, Hokkaido Research Organization , 085-8588 Hokkaido , Japan (MU)
| | - Mayumi Ueno
- Yamanashi Forest Research Institute , 2290-1, Saishoji, Fujikawa, Yamanashi 400-0502 , Japan (HI).,Eastern Field Station, Institute of Environmental Sciences, Hokkaido Research Organization , 085-8588 Hokkaido , Japan (MU)
| |
Collapse
|
39
|
Cruz-Rodríguez JA, González-Machorro E, Villegas González AA, Rodríguez Ramírez ML, Mejía Lara F. Autonomous Biological Control of Dactylopius opuntiae (Hemiptera: Dactyliiopidae) in a Prickly Pear Plantation With Ecological Management. Environ Entomol 2016; 45:642-648. [PMID: 27055467 DOI: 10.1093/ee/nvw023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 03/04/2016] [Indexed: 06/05/2023]
Abstract
It is broadly known that the conservation of biological diversity in agricultural ecosystems contributes to pest control. This process was studied in a prickly pear plantation (Opuntia megacantha and Opuntia ficus-indica) located in central Mexico. No insecticides have been used on this plantation since 2000, and local farmers believe that the presence of different species of insects limits the growth of the wild cochineal (Dactylopius opuntiae Cockerell), which is one of the main pests in this crop. From August 2012 to November 2013, we estimated the number of cochineal per stem in the plantation and determined its spatial distribution pattern. In order to identify signs of population regulation, we obtained histograms of the frequency distribution of the size of the clusters and determined if distribution is adjusted to a power function (power law). We identified the cochineal predators and determined the correlation in their abundances. The greater abundance of cochineal occurred between summer and autumn while the minimum value was recorded in spring. The frequency distribution of the cochineal clusters had a high level of adjustment to a power function, suggesting the presence of population regulation processes. Six species that prey on cochineal were identified. Laetilia coccidivora and Hyperaspis trifurcata were the most active and their abundance was significantly correlated with the abundance of cochineal. We found that the probability of extinction of these insects in a cladode increases with its density, since the density and predator activity also increased. It is likely that, under these conditions, the cochineal have established an autonomous control.
Collapse
Affiliation(s)
- J A Cruz-Rodríguez
- 1Departmento de Agroecología, Universidad Autónoma Chapingo. Km 38.5 de la carretera México-Texcoco, Estado de México, México (; ; )
| | - E González-Machorro
- 1Departmento de Agroecología, Universidad Autónoma Chapingo. Km 38.5 de la carretera México-Texcoco, Estado de México, México (; ; )
| | - A A Villegas González
- 1Departmento de Agroecología, Universidad Autónoma Chapingo. Km 38.5 de la carretera México-Texcoco, Estado de México, México (; ; )
| | | | - F Mejía Lara
- 3Área de Biología. Universidad Autónoma Chapingo. Km 38.5 de la carretera México-Texcoco, Estado de México, México
| |
Collapse
|
40
|
Abstract
Pathogens are ubiquitous in insect populations and yet few studies examine their dynamics and impacts on host populations. We discuss four lepidopteran systems and explore their contributions to disease ecology and evolution. More specifically, we elucidate the role of pathogens in insect population dynamics. For three species, western tent caterpillars, African armyworm and introduced populations of gypsy moth, infection by nucleopolyhedrovirus (NPV) clearly regulates host populations or reduces their outbreaks. Transmission of NPV is largely horizontal although low levels of vertical transmission occur, and high levels of covert infection in some cases suggest that the virus can persist in a nonsymptomatic form. The prevalence of a mostly vertically transmitted protozoan parasite, Ophryocystis elektroscirrha, in monarch butterflies is intimately related to their migratory behaviour that culls highly infected individuals. Virulence and transmission are positively related among genotypes of this parasite. These systems clearly demonstrate that the interactions between insects and pathogens are highly context dependent. Not only is the outcome a consequence of changes in density and genetic diversity: environmental factors, particularly diet, can have strong impacts on virulence, transmission and host resistance or tolerance. What maintains the high level of host and pathogen diversity in these systems, however, remains a question.
Collapse
Affiliation(s)
- Judith H. Myers
- Department of ZoologyUniversity of British ColumbiaVancouverBCCanada
| | - Jenny S. Cory
- Department of Biological SciencesSimon Fraser UniversityBurnabyBCCanada
| |
Collapse
|
41
|
Sussky EM, Elkinton JS. Survival and Near Extinction of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) During Summer Aestivation in a Hemlock Plantation. Environ Entomol 2015; 44:153-159. [PMID: 26308818 DOI: 10.1093/ee/nvu007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Accepted: 10/08/2014] [Indexed: 06/04/2023]
Abstract
Varying densities of the spring generation of the hemlock woolly adelgid were manipulated on 16 previously uninfested eastern hemlocks in an open-field plantation in Massachusetts. In contrast to experimentally created hemlock woolly adelgid populations in a forest, as reported previously, there was no evidence of density-dependent survival on a tree-wide basis in the plantation in the spring (progrediens) generation. There was, however, comparable density-dependent survival of settled crawlers and sexupara production when samples of the population were examined from branches with high density. Plantation hemlocks had 9.3 times more foliage and 10 times lower adelgid densities per cm than the forest hemlocks. These results show that density-dependent processes in the progrediens generation may only be evident when hemlock woolly adelgid density reaches a critical threshold. In the sistens generation that begins in midsummer, we counted a mean of 126 settled crawlers on marked branch on all 16 trees, but none of these adelgids survived the mid-summer aestivation phase, perhaps due to higher temperatures that were recorded in the plantation compared with a nearby hemlock forest, where 16% of the adelgids survived the aestivation phase. Whole tree counts of overwintering adelgids revealed that the adelgid populations had gone extinct on 13 out of the 16 trees. Mortality in the midsummer aestivation phase often exceeds overwintering mortality that has been widely thought to be the main factor that limits adelgid population growth and spread, particularly in northern states.
Collapse
Affiliation(s)
- Elizabeth M Sussky
- Graduate program in Entomology, Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, MA 01003
| | - Joseph S Elkinton
- Graduate program in Entomology, Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, MA 01003, Graduate program in Entomology, Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, MA 01003,
| |
Collapse
|
42
|
Abstract
A long-standing aim of ecologists is to understand the processes involved in regulating populations. One such mechanism is the buffer effect, where lower quality habitats are increasingly used as a species reaches higher population densities, with a resultant average reduction in fecundity and survival limiting population growth. Although the buffer effect has been demonstrated in populations of a number of species, a test of its importance in influencing population growth rates of multiple species across large spatial scales is lacking. Here, we use habitat-specific population trends for 85 bird species from long-term national monitoring data (the UK Breeding Bird Survey) to examine its generality. We find that both patterns of population change and changes in habitat preference are consistent with the predictions of the buffer effect, providing support for its widespread operation.
Collapse
Affiliation(s)
| | - Stuart E Newson
- British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK
| | | |
Collapse
|
43
|
Starns HD, Weckerly FW, Ricca MA, Duarte A. Vegetation changes associated with a population irruption by Roosevelt elk. Ecol Evol 2015; 5:109-20. [PMID: 25628868 PMCID: PMC4298438 DOI: 10.1002/ece3.1327] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 11/04/2014] [Accepted: 11/05/2014] [Indexed: 11/17/2022] Open
Abstract
Interactions between large herbivores and their food supply are central to the study of population dynamics. We assessed temporal and spatial patterns in meadow plant biomass over a 23-year period for meadow complexes that were spatially linked to three distinct populations of Roosevelt elk (Cervus elaphus roosevelti) in northwestern California. Our objectives were to determine whether the plant community exhibited a tolerant or resistant response when elk population growth became irruptive. Plant biomass for the three meadow complexes inhabited by the elk populations was measured using Normalized Difference Vegetation Index (NDVI), which was derived from Landsat 5 Thematic Mapper imagery. Elk populations exhibited different patterns of growth through the time series, whereby one population underwent a complete four-stage irruptive growth pattern while the other two did not. Temporal changes in NDVI for the meadow complex used by the irruptive population suggested a decline in forage biomass during the end of the dry season and a temporal decline in spatial variation of NDVI at the peak of plant biomass in May. Conversely, no such patterns were detected in the meadow complexes inhabited by the nonirruptive populations. Our findings suggest that the meadow complex used by the irruptive elk population may have undergone changes in plant community composition favoring plants that were resistant to elk grazing.
Collapse
Affiliation(s)
- Heath D Starns
- Department of Biology, Texas State UniversitySan Marcos, Texas, 78666
| | - Floyd W Weckerly
- Department of Biology, Texas State UniversitySan Marcos, Texas, 78666
| | - Mark A Ricca
- U.S. Geological Survey, Western Ecological Research Center800 Business Park Drive, Suite D, Dixon, California, 95620
| | - Adam Duarte
- Department of Biology, Texas State UniversitySan Marcos, Texas, 78666
| |
Collapse
|
44
|
Fischer S, Sy V, Campos RE, Otero M. Effects of Larval Density and Habitat Drying on Developmental Success of Ochlerotatus albifasciatus (Diptera: Culicidae) in Urban Rain Pools: Evidence From Field and Experimental Studies. J Med Entomol 2014; 51:1175-1181. [PMID: 26309304 DOI: 10.1603/me14020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 08/27/2014] [Indexed: 06/04/2023]
Abstract
Ochlerotatus albifasciatus (Macquart) (Diptera: Culicidae) larvae develop synchronously after rainfall events in ephemeral or temporary pools, where they occasionally attain very high abundance. The aims of the current study were to analyze the response of life history parameters such as daily larval mortality, time to pupation, and adult size of Oc. albifasciatus to increasing larval density under controlled conditions, and to analyze the relationships of daily larval mortality with density and environmental variables (drying rate, temperature, and season) in urban rain pools in Buenos Aires, Argentina. An exponential increase in mortality was observed at high larval densities under controlled conditions. Development times and adult size (wing length) differed between males and females, and were also affected by density. Development times extended for 0.36 d for each order of magnitude of increase in larval density, and wing length decreased 0.0021 mm per additional larva in 600 cm(2). Larval density in the field varied from <1 larva per square meter to nearly 1100 larvae per square meter. Daily larval mortality values in the field were variable (0.02-0.91), positively related to the drying rate, and exhibited seasonal differences. No significant relation with larval density or temperature was found in the field. It remains to be established whether the density-independent mortality observed in this study is a generalized pattern of Oc. albifasciatus populations in Buenos Aires Province or a pattern restricted only to urban habitats.
Collapse
Affiliation(s)
- S Fischer
- Departamento de Ecología, Genética y Evolución, and Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Ciudad Universitaria, Pabellón 2, 4to piso. Laboratorio 54. C1428EHA, Buenos Aires, Argentina.
| | - V Sy
- Instituto de Limnología "Dr. Raúl A. Ringuelet", Universidad Nacional de La Plata - CONICET, CCT La Plata, Boulevard 120 y 62 - Casilla de Correo N° 712. 1900, La Plata, Buenos Aires, Argentina. Instituto de Recursos Minerales (Universidad Nacional de La Plata-CIC), Calle 64 entre 119 y 120 s/n°. B1904DZB, La Plata, Buenos Aires, Argentina
| | - R E Campos
- Instituto de Limnología "Dr. Raúl A. Ringuelet", Universidad Nacional de La Plata - CONICET, CCT La Plata, Boulevard 120 y 62 - Casilla de Correo N° 712. 1900, La Plata, Buenos Aires, Argentina
| | - M Otero
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, and IFIBA (CONICET-UBA), Argentina. Ciudad Universitaria, Pabellón 1, 2do piso. C1428EHA, Buenos Aires, Argentina
| |
Collapse
|
45
|
Jansen PA, Visser MD, Joseph Wright S, Rutten G, Muller-Landau HC. Negative density dependence of seed dispersal and seedling recruitment in a neotropical palm. Ecol Lett 2014; 17:1111-20. [PMID: 25039608 DOI: 10.1111/ele.12317] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/16/2014] [Accepted: 05/31/2014] [Indexed: 11/29/2022]
Abstract
Negative density dependence (NDD) of recruitment is pervasive in tropical tree species. We tested the hypotheses that seed dispersal is NDD, due to intraspecific competition for dispersers, and that this contributes to NDD of recruitment. We compared dispersal in the palm Attalea butyracea across a wide range of population density on Barro Colorado Island in Panama and assessed its consequences for seed distributions. We found that frugivore visitation, seed removal and dispersal distance all declined with population density of A. butyracea, demonstrating NDD of seed dispersal due to competition for dispersers. Furthermore, as population density increased, the distances of seeds from the nearest adult decreased, conspecific seed crowding increased and seedling recruitment success decreased, all patterns expected under poorer dispersal. Unexpectedly, however, our analyses showed that NDD of dispersal did not contribute substantially to these changes in the quality of the seed distribution; patterns with population density were dominated by effects due solely to increasing adult and seed density.
Collapse
Affiliation(s)
- Patrick A Jansen
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama; Department of Environmental Sciences, Wageningen University, PO Box 47, 6700 AA, Wageningen, The Netherlands; Community and Conservation Ecology group, University of Groningen, PO Box 11103, 9700 CC, Groningen, The Netherlands
| | | | | | | | | |
Collapse
|
46
|
Cubaynes S, MacNulty DR, Stahler DR, Quimby KA, Smith DW, Coulson T. Density-dependent intraspecific aggression regulates survival in northern Yellowstone wolves (Canis lupus). J Anim Ecol 2014; 83:1344-56. [PMID: 24749694 DOI: 10.1111/1365-2656.12238] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 04/11/2014] [Indexed: 11/30/2022]
Abstract
Understanding the population dynamics of top-predators is essential to assess their impact on ecosystems and to guide their management. Key to this understanding is identifying the mechanisms regulating vital rates. Determining the influence of density on survival is necessary to understand the extent to which human-caused mortality is compensatory or additive. In wolves (Canis lupus), empirical evidence for density-dependent survival is lacking. Dispersal is considered the principal way in which wolves adjust their numbers to prey supply or compensate for human exploitation. However, studies to date have primarily focused on exploited wolf populations, in which density-dependent mechanisms are likely weak due to artificially low wolf densities. Using 13 years of data on 280 collared wolves in Yellowstone National Park, we assessed the effect of wolf density, prey abundance and population structure, as well as winter severity, on age-specific survival in two areas (prey-rich vs. prey-poor) of the national park. We further analysed cause-specific mortality and explored the factors driving intraspecific aggression in the prey-rich northern area of the park. Overall, survival rates decreased during the study. In northern Yellowstone, density dependence regulated adult survival through an increase in intraspecific aggression, independent of prey availability. In the interior of the park, adult survival was less variable and density-independent, despite reduced prey availability. There was no effect of prey population structure in northern Yellowstone, or of winter severity in either area. Survival was similar among yearlings and adults, but lower for adults older than 6 years. Our results indicate that density-dependent intraspecific aggression is a major driver of adult wolf survival in northern Yellowstone, suggesting intrinsic density-dependent mechanisms have the potential to regulate wolf populations at high ungulate densities. When low prey availability or high removal rates maintain wolves at lower densities, limited inter-pack interactions may prevent density-dependent survival, consistent with our findings in the interior of the park.
Collapse
Affiliation(s)
- Sarah Cubaynes
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - Daniel R MacNulty
- Department of Wildland Resources, Utah State University, Logan, UT, 84322, USA
| | - Daniel R Stahler
- Yellowstone Wolf Project, Yellowstone Center for Resources, Yellowstone National Park, Mammoth, WY, 82190, USA
| | - Kira A Quimby
- Yellowstone Wolf Project, Yellowstone Center for Resources, Yellowstone National Park, Mammoth, WY, 82190, USA
| | - Douglas W Smith
- Yellowstone Wolf Project, Yellowstone Center for Resources, Yellowstone National Park, Mammoth, WY, 82190, USA
| | - Tim Coulson
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| |
Collapse
|
47
|
López-Bao JV, Rodríguez A, Delibes M, Fedriani JM, Calzada J, Ferreras P, Palomares F. Revisiting food-based models of territoriality in solitary predators. J Anim Ecol 2014; 83:934-42. [PMID: 24720673 DOI: 10.1111/1365-2656.12226] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 04/02/2014] [Indexed: 11/30/2022]
Abstract
Food availability is considered a major factor determining spacing behaviour in territorial species, especially for females. Theoretically, spatial overlap (considered the opposite of territoriality) and food availability are related in a nonlinear manner (hypothesized inverted-U function), with high overlap levels at the extremes of a food availability gradient and low overlap at intermediate levels of this gradient. Similar patterns are expected for encounter frequencies owing to its expected correlation with spatial overlap. However, these predictions have rarely been tested in highly structured social systems on a broad gradient of food availability, which implicitly requires experimental manipulation. We test these predictions in a solitary, territorial and trophic specialist, the Iberian lynx Lynx pardinus, taking advantage of a three-decade data set of spatial behaviour in different scenarios of food availability (i.e. rabbit density). In contrast with expectations, home range overlap among resident females was low (median overlap index = 0.08, range 0-0.57) and core area overlap was nearly nil (median overlap index = 0, range 0-0.22) throughout the entire gradient of prey availability. Furthermore, spatial associations between pairs of females were negligible regardless marked variation in prey availability. Therefore, we did not find support for a model of flexible lynx territoriality driven by food availability. Our results suggest that the exclusive use of space in the Iberian lynx was not related to food. Lack of influence of prey availability on lynx territoriality may be adaptive to cope with the consequences of frequent drought-induced periods of prey scarcity or other disturbance typically affecting wild rabbit populations in Mediterranean environments. Thus, lynx would adopt an obstinate strategy of territoriality that consists in defending exclusive areas across a broad range of resource availability ensuring an exclusive access to the minimum amount of prey necessary for survival and eventually reproduction even during periods of prey scarcity. However, we found signs that territoriality was influenced by lynx density in a nonlinear fashion. Our results suggest the occurrence of population regulation through territoriality in this species.
Collapse
Affiliation(s)
- José V López-Bao
- Research Unit of Biodiversity (UO/CSIC/PA), Oviedo University, Mieres, 33600, Spain.,Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences (SLU), Riddarhyttan, SE-730 91, Sweden
| | - Alejandro Rodríguez
- Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Seville, 41092, Spain
| | - Miguel Delibes
- Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Seville, 41092, Spain
| | - José M Fedriani
- Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Seville, 41092, Spain
| | - Javier Calzada
- Departamento de Biología Ambiental y Salud Pública, Universidad de Huelva, Huelva, 21071, Spain
| | - Pablo Ferreras
- Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC-UCLM-JCCM), Ciudad Real, 13005, Spain
| | - Francisco Palomares
- Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Seville, 41092, Spain
| |
Collapse
|
48
|
Krkošek M, Revie CW, Finstad B, Todd CD. Comment on Jackson et al. 'impact of Lepeophtheirus salmonis infestations on migrating Atlantic salmon, Salmo salar L., smolts at eight locations in Ireland with an analysis of lice-induced marine mortality'. J Fish Dis 2014; 37:415-417. [PMID: 23941243 DOI: 10.1111/jfd.12157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 05/28/2013] [Indexed: 06/02/2023]
Affiliation(s)
- M Krkošek
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | | | | | | |
Collapse
|
49
|
Wakefield ED, Phillips RA, Matthiopoulos J. Habitat-mediated population limitation in a colonial central-place forager: the sky is not the limit for the black-browed albatross. Proc Biol Sci 2014; 281:20132883. [PMID: 24430849 DOI: 10.1098/rspb.2013.2883] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Animal populations are frequently limited by the availability of food or of habitat. In central-place foragers, the cost of accessing these resources is distance-dependent rather than uniform in space. However, in seabirds, a widely studied exemplar of this paradigm, empirical population models have hitherto ignored this cost. In part, this is because non-independence among colonies makes it difficult to define population units. Here, we model the effects of both resource availability and accessibility on populations of a wide-ranging, pelagic seabird, the black-browed albatross Thalassarche melanophris. Adopting a multi-scale approach, we define regional populations objectively as spatial clusters of colonies. We consider two readily quantifiable proxies of resource availability: the extent of neritic waters (the preferred foraging habitat) and net primary production (NPP). We show that the size of regional albatross populations has a strong dependence, after weighting for accessibility, on habitat availability and to a lesser extent, NPP. Our results provide indirect support for the hypothesis that seabird populations are regulated from the bottom-up by food availability during the breeding season, and also suggest that the spatio-temporal predictability of food may be limiting. Moreover, we demonstrate a straightforward, widely applicable method for estimating resource limitation in populations of central-place foragers.
Collapse
Affiliation(s)
- Ewan D Wakefield
- British Antarctic Survey, Natural Environment Research Council, , High Cross, Madingley Road, Cambridge CB3 0ET, UK, Scottish Oceans Institute, School of Biology, University of St Andrews, , Fife KY16 8LB, UK, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, , Glasgow G12 8QQ, UK
| | | | | |
Collapse
|
50
|
Greenberg DA, Green DM. Effects of an invasive plant on population dynamics in toads. Conserv Biol 2013; 27:1049-1057. [PMID: 23692126 DOI: 10.1111/cobi.12078] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 12/20/2012] [Indexed: 06/02/2023]
Abstract
When populations decline in response to unfavorable environmental change, the dynamics of their population growth shift. In populations that normally exhibit high levels of variation in recruitment and abundance, as do many amphibians, declines may be difficult to identify from natural fluctuations in abundance. However, the onset of declines may be evident from changes in population growth rate in sufficiently long time series of population data. With data from 23 years of study of a population of Fowler's toad (Anaxyrus [ = Bufo] fowleri) at Long Point, Ontario (1989-2011), we sought to identify such a shift in dynamics. We tested for trends in abundance to detect a change point in population dynamics and then tested among competing population models to identify associated intrinsic and extrinsic factors. The most informative models of population growth included terms for toad abundance and the extent of an invasive marsh plant, the common reed (Phragmites australis), throughout the toads' marshland breeding areas. Our results showed density-dependent growth in the toad population from 1989 through 2002. After 2002, however, we found progressive population decline in the toads associated with the spread of common reeds and consequent loss of toad breeding habitat. This resulted in reduced recruitment and population growth despite the lack of significant loss of adult habitat. Our results underscore the value of using long-term time series to identify shifts in population dynamics coincident with the advent of population decline.
Collapse
Affiliation(s)
- Daniel A Greenberg
- Redpath Museum, McGill University, 859 Sherbrooke Street W., Montreal, Quebec H3A 0C4, Canada
| | | |
Collapse
|